Modeling of Species Transport and Macrosegregation in Heavy Steel Ingots
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HEAVY steel ingots are typically used to manufacture mill rolls, pressure vessels, and turbine rotor shafts in metallurgy, petrochemistry, energy, and other heavy industries. Macrosegregation is a major defect in these large ingots. It seriously deteriorates material homogeneity and thus affects the final properties and the performance of the key forging components manufactured. Multiple pouring (MP) process[1,2] is widely used to minimize macrosegregation in large ingots (e.g., 100 to 670 tons). It sequentially pours molten steel using different ladle compositions. It has been recognized that carbon concentration distribution in the ingot at the end of the MP process is crucial for the macrosegregation
WENSHENG LI, formerly Ph.D. Student with the Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People’s Republic of China, is now Engineer with Electric Power Research Institute of Guangdong Power Grid Corporation, Guangzhou 510080, People’s Republic of China. HOUFA SHEN and BAICHENG LIU, Professors, are with the School of Materials Science and Engineering, Tsinghua University. Contact e-mail: [email protected] XIONG ZHANG, formerly Graduate Student with the Department of Mechanical Engineering, Tsinghua University, is now Assistant Engineer with Sinotrans Ltd., Beijing 100044, People’s Republic of China. Manuscript submitted January 26, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
formation in the subsequent solidification process. However, few numerical or experimental studies of species transport during the MP process of large ingots have been reported in the literature. On the other hand, modeling of macrosegregation formation during industrial steel ingot solidification is still challenging.[3–5] In the last two decades, multiphase solidification models have been developed to predict macrosegregation. Beckermann and co-workers[4,6,7] first proposed a multiphase model that accounts for melt convection and grain motion. Ludwig and co-workers[8–11] developed a series of sophisticated multiphase models. A pioneering application of these multiphase models to industry-scale steel ingots has been performed recently by Combeau and co-workers.[12–15] Macrosegregations in ingots of 3.3 and 6.2 ton were experimentally measured and numerically simulated in their study. Most recently, Combeau and co-workers[16] applied a multiphase model to a 65-ton steel ingot. Simulation results of macrosegregation in the ingot were compared with experiments. The authors pointed out: ‘‘These results are encouraging and show that the model is on the good way for being fully predictive.’’ They also claimed that the model needed to be further improved. Recent progress made by the authors of the current study on numerical modeling of species transport and macrosegregation in heavy steel ingots is reported in this article. A ladle–tundish–mold species transport model for the MP process is first applied to a 292-ton steel ingot. Simulation results of macrosegregation formation during the solidification process of a 53
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